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The Equipment
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Seen above is one of our systems that uses a closed cycle helium cryostat (a kind of fridge that uses Helium in the compressor in place of freon. This one is used by Drs. Elsila and Bernstein to study the photochemistry of PAHs and related molecules frozen at very low temperature in water ice, of the kind seen in dense interstellar clouds, comets and on Europa the icy moon of Jupiter. A close up of the business end can be seen below.
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This is a close up shot looking into the vacuum chamber seen above. This picture was taken by Dr. Elsila while she was exposing an H2O quinoline mixture to UV photolysis. The pink glow comes from her hydrogen lamp. Quinoline is an interesting organic molecule that has been detected in meteorites, and if you want to learn more about it you can see her poster at the upcoming NAI meeting in Boulder.
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The Interstellar Simulation Chamber (above) is a new facility in the UV-Visible Astrochemistry Laboratory that allows scientists (such as Dr. Salama in collaboration with Los Gatos Research)to measure the spectra of molecules and ions in the gas-phase, but at extremely low temperatures and with very high sensitivities using a variety of cavity ringdown techniques.
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Above is a picture of the high vacuum system and cryostat in the UV-Visible Astrochemistry Laboratory that is fit with the manual liquid Helium transfer line. With this set-up itis possible to go as cold as 4 K, just four degrees above absolute zero! (that's almost - 270 Cor -450 F). Scientists (Drs. Halasinski and Salama) use it to take UV - NIR spectra of PAHs and PAH ions in solid Ne, and these are compared to astronomical data.
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Above is a closer look at the window at the center of one of these vacuum systems. You are looking in the side of the vacuum system, through an outer window where a laser, IR, or UV light would shine. Inside the vacuum system is another window in a black frame (illuminated by blue light) and it is on this smaller innner window that the sample is prepared. Off to the right the thing that looks like its wrapped in gauze is a pyrex tube containing a sample of PAH. The wrap is heat tape, heating is needed to sublime the sample.
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Above is a picture of one of our conventional systems that uses a closed cycle cryostat and goes to about 10 K. We have three such systems and these are used for infrared spectroscopy of ices and PAHs.In these pictures above you may have noticed the glass bulbs wrapped in yellow or black tape. These contain mixtures of gases that we depoist onto the CsI windows at low temperature, where they freeze solid. We mix these gases in a large glass line...
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The glass line, above, is attached to a diffusion (vacuum) pump and has many openings so that many different compounds can be mixed together. We often mix simple molecules like water, carbon dioxide, carbon monoxide, and ammonia together in order to make samples that approximate the ices seen in comets and frozen on interstellar grains.
Before we can introduce liquids like water into our samples we have to remove the gases, and we do that on the glass line, above, by freezing it on liquid nitrogen and pumping away the gases but leaving the frozen liquid behind. The freezing process drives the gases out of the freezing liquid. Above is a picture of a water finger being frozen. If you look closely you can see bubbles of air sitting just at the solid-liquid interface.
